Common Ground Public Art Mosaic Tables

Materials and Methods for Outdoor Mosaic Tables

Artist Risa Puno recently completed her interactive mosaic sculpture Common Ground for Rufus King Park in Jamaica Queens, NYC, and the project is a great example for discussing materials and methods for mosaic table tops.

No Plywood Backers Outdoors

Plywood is never an acceptable backer for outdoor mosaic table tops.

Humidity in outdoor air can cause plywood to swell, contract, and warp, and even if the displacement is too small to be noticed, it can still cause grout to crack and tiles to pop off. Once grout has hairline cracks, moisture can penetrate underneath, and then there isn’t any hope for the mosaic lasting after that happens.

If you have a wooden table that you want to mosaic for outdoors, then attach a piece of 1/4-inch concrete backer board over the top of the wood and mosaic on that. 

Seal your finished outdoor mosaic with a tile and grout sealer and reseal it each fall. Silicone-based gout sealers are wipe-on-wipe-off and easy to apply. Most of the work is buffing off the excess so that the surfaces are slippery.

Custom Mosaic Table Top Backers

Kerdi Board Tile Backer
Kerdi Board Tile Backer by Schluter is hard expanded polystyrene. It can be cut quickly and easily with an ordinary circular saw or table saw. This image stolen shamelessly by Evil Joe from the Schluter website.

Foam Core Board

One option for outdoor mosaic table tops is to use a piece of foam-core board such as used to fabricate bathroom surfaces. This hard expanded polystyrene board is water resistant and can be cut quickly by scoring with a box cutter and snapping. Brands of foam-core backer board include Durock and KerdiBoard.

The issue with these foam-core boards is what to do about the edges. Since you will be using thinset mortar to mount the tiles, you could use thinset with hardware cloth (metal mesh) or fiberglass mesh to plaster over the top and wrap around the edges. Of course, this work would need to be done a few days before mosaicing to allow it to harden because thinset contracts or “shrinks” slightly as it hardens.

I think Risa decided not to use foam core board for her project because she didn’t have time to fully evaluate how flexible it was and how it might need to be supported. Also, she wanted to make sure the tables were as strong and as impact resistant as possible since they would literally be walked on as part of a piece of sculpture open to the general public.

From my experience with hard expanded polystyrene, it’s more than tough enough for home table use, and as long as you supported it along the edges and at the center, it should provide a stiff unbending surface. Of course, you would need to use the 1.5 inch or 2 inch thickness or laminate two thinner pieces together.

What About Edges?

In theory, the easiest treatment for edges is a metal rim, but most crafters are not welders or metal workers. And so, if your table doesn’t already include a metal rim, then your best option is to fabricate a table top that has a wide edge and mosaic the edge like Risa did in her project.

Yes, mosaiced edges can make the top more vulnerable to damage, and so consider the type of chairs that will be pushed up against it and other usage issues.

Mosaic Table Top
Mosaic Table Top fabricated from 1/2-inch concrete backer board over plywood. Note the fastener used to attach the corner piece. The fastener augments the adhesive or thinset that was also used to attach the concrete board.

Concrete Board over Plywood

For Risa’s project, she chose to fabricate her table tops from CDX plywood with a layer of 1/2-inch concrete backer board attached to the top and sides. The concrete board was attached with thinset mortar and fasteners (special screws with custom heads designed to hold concrete board). Purchase these fasteners at the same building material store where you buy the concrete board.

Once the concrete board was in place, then hardware cloth (metal mesh) was plastered over the top with thinset mortar to form a shell.

Note how Risa chose to blunt her corners with a short diagonal nose. This goes a long way toward reducing the potential for damage, which usually happens at corners when people bump the table top and knock off a tile or two. This also eliminates people getting poked in the hip or shins by sharp corners.

The undersides of these table tops are CDX plywood, and these were sealed with multiple coats of an exterior deck sealer.

Table Bases

Make sure your table base can support the weight of a mosaic table top. Also make sure that the table isn’t top heavy and unstable and prone to falling over. We prefer and recommend wider tables with lower centers of gravity for mosaic surfaces.

Interlocked frame for supporting mosaic table top surfaces
Interlocked frame for supporting mosaic table top surfaces at different heights as part of the Common Ground interactive public art installation. I would use pressure treated lumber with multiple coats of sealant for a wooden table base for a home project and reinforced concrete for a permanent installation. I think Risa told me that this installation would be in place for one year. For stuff on your patio, clean, and reseal each year in the fall.


Important Caveats

For a piece of public art, you need to make sure you are using architectural materials and methods and not information recommended for crafters making mosaic tables for their home patios.

Keep in mind that there is a lot of advice online that doesn’t make sense in terms of longevity even for backyard projects. Too many people think in terms of everything being temporary and disposable, and then there are other people who just want to sell stuff, and so you have to vet what you read online.

At Mosaic Art Supply, we do our best to recommend methods that are suitable for architectural use and rely on best practices. I am an engineer by training and experience, and my employees are professional artists who emphasize quality and durability in their own work.

For a permanent installation for something like this, you would need to use a base of reinforced concrete or maybe slabs of granite and include vertical surfaces to prevent people from slipping between surfaces. You would also need to prevent the sh*thead variety of skateboarder from damaging it by making a cement border on outside edges and include slide blocks.

For a permanent installation, I would bow horizontal surfaces slightly to allow for drainage, which will increase the life of the mosaic, especially if annual cleaning and sealing are neglected in the future.


Artist Risa Puno With Mosaic Table Top
Artist Risa Puno With Mosaic Table Top

Tips for Increased Durability

Glass tile is impervious to liquids and therefore frost proof. The points of vulnerability are the grout line and the cement used to attach the tiles. You can make those a lot more freeze resistant by sealing with multiple applications of a tile and grout sealer, and resealing each year. Wipe away excess completely so that it isn’t a slip hazard and follow the instructions on the can.

For your grout, consider using epoxy-based grouts, which are much stronger than traditional grouts. We have no experience with these because we use traditional materials and methods because we are making heirloom art and fine art, and so we think in terms of archival properties.

We use sanded grout for all our grouted mosaics. Non-sanded grout is for hairline cracks or mixing with sand. Non-sanded grout will be fragile in gaps of any width.

Avoid silicone caulk in your mosaic work. Sure it is waterproof, but it is flexible, but grout is not. It is also is messy to work with, and it doesn’t clean up easily with soap and water.



44 responses to “Materials and Methods for Outdoor Mosaic Tables”

  1. Pauline Stickler Avatar
    Pauline Stickler

    I wanted to let you know that there is software for resizing patterns for mosacing. It is called “Rapid Resizer” and it works great! Enjoy!!

    1. Joe Moorman Avatar
      Joe Moorman

      Thanks Pauline! I haven’t used it. I suspect it costs more than a ruler and pencil, but for murals or other large complicated mosaic, it might be well worth it.

  2. Yvonne Ramsey Avatar
    Yvonne Ramsey

    I just posted and am trying to send a picture of my wall Is there a way to send it to you?

    Also I am H.S. Teacher and we are starting an Club called “Art Legacy” the mission will to use the campus as a canvas . We have 2 projects in mind this year and are fund raising to cover costs. 1st is to start an art garden, initial installations will be stepping stones. (this way I can teach the kids techniques and design lessons on a smaller scale) The stones will represent graduating classes, clubs and school funding donors.
    Our bigger mosaic will be on the face of a set of stairs. Have any thoughts for me as we haven’t yet begun still getting funding for supplies.

    1. Joe Moorman Avatar
      Joe Moorman

      Sure thing! Please email us the picture.

  3. Sandra Nelsen Avatar
    Sandra Nelsen

    Hey Joe, thanks for all of your informative posts, very helpful! I have a question about silicone caulk. I have used this to attach tile to Wedi Board with traditional sanded grout on exterior public installations in Colorado with fairly good success. They are vertical installations so don’t have the threat of water or snow sitting on them. Have you had problems with silicone caulking for attaching tiles? And second, what type of adhesive would you suggest?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Sandra,
      For outdoor and wet mosaics, we use thinset mortar instead of adhesives. The reason we discourage silicone caulk is that it is flexible but grout is not, and so people who use it often have problems with the grout cracking because the tiles moves slightly when pressed. I have to admit that I would probably use silicone caulk if I couldn’t use thinset, and so that is the adhesive that I would use, but I wouldn’t be enthusiastic about it. I don’t like using anything that can’t be cleaned up easily with water, especially when it is sticky and messy like caulk.

  4. mara Avatar


    Am planning to make several portuguese tile tables, since i have a whole load of them.
    Did some mosaic on wood in the past, but i want to make outdoor tables.
    My plan is to ask the local welder to make the tabletop with edges.
    I wonder now how thick the metal plate needs to be, in order to be stable.
    Thanks in advance,

  5. mara Avatar

    Am speaking with a welder to make a table to put portuguese tiles on.
    How thick do you think the metal top needs to be?
    Thank you loads

    1. Joe Moorman Avatar
      Joe Moorman


      Metal isn’t a good backer for mosaics. The frame of the table should be metal, but the top should be an insert of Hardiboard or cement backer board.

  6. Judy snively Avatar
    Judy snively

    What type of cutters should I use to cut the Iridecent glass tile we ordered from Mosaic Art Supply….

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Judy,

      You should use a Mosaic Glass Cutter.


  7. Bill Avatar

    Recommendations for waterproofing table top with small pieces ie products. Also what about Grout Boost?

    1. Joe Moorman Avatar
      Joe Moorman

      I’m not familiar with that product. It sounds like a polymer additive for increased strength or maybe a sealer of some kind. We use ordinary tile and grout sealers.


  8. Mataiasi Turagava Avatar

    It is my very first time creating MOSAIC TABLES, and I really love it. Just the bright clours you may use.

  9. CarolynAnn Straub Avatar
    CarolynAnn Straub

    As a beginner with mosaic glass, I deeply appreciate your guidance. Thank you!

    I’m planning to do a glass mosaic on a 17” glass table for my deck.

  10. Paulette Warren Avatar
    Paulette Warren

    I purchased some thick ceramic tiles in Mexico that I want to put on a vertical plywood surface that would then be hung on an indoor wall. The tiles will butt up against each other, no grouting between tiles. I will pretreat the plywood with Weldbond. I would like to have a recommendation for best adhesive to use in this situation. I am considering Welbod adhesive; 100 percent silicone adhesive; or thin set. There will e a glass tile border. Please advise best possible adhesion or any other suggestions. Thanks you.

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Paulette,

      Weldbond is the best of that: strong, archival, and water based. There isn’t any need to preseal.


      1. Paulette Warren Avatar
        Paulette Warren

        Thanks so much for your prompt response. Much appreciated.

  11. Jim Baird Avatar
    Jim Baird

    I and my wife have begun to cover a 24″ diameter red oak stump, cut off a year ago, de-barked, and belt sanded, with a slight crown and good slope for drainage. Have you known any success with that kind of back? Using thinset and your soft shapes, some of the area has been covered and is hanging on.

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Jim,

      Not really. Wood swells and contracts slightly with daily changes in humidity, and so it is only a matter of time before the mosaic falls off. Fortunately, you have red oak, and you put a slope on it.

  12. elena Avatar

    I would like to mosaic an outdoor table. The legs are iron, but the top is wood veneer. I would like to make a new top. I would appreciate your advice if I could use Home Depo’s “3/4 in. x 4 ft. x 8 ft. Ground Contact Pressure Treated Pine Performance Rated Sheathing (2X the protection compared to Above Ground treatment: Treated for protection against fungal decay, rot and termites. Ideal for decks, walkways, landscaping and other outdoor projects)” without any additional backing?

    Thank you!

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Elena,
      You would be much better off using HardieBacker cement backer board. Thanks!

      1. Elena Avatar

        Thank you, Joe, so much for your quick response!

  13. Lisa Avatar

    This will be my first mosaic project. I am wanting to mosaic on top of an outdoor concrete table. The table top looks like it has little pebbles on it, so it’s not smooth. Can I mosaic right over the top or do I need to attach backer board? What is the best way to do this?

    1. Joe Moorman Avatar
      Joe Moorman

      I smooth outdoor surfaces by plastering with thinset mortar a few days before I mosaic.

      1. Lisa Avatar

        That was my plan – just wanted to confirm. Thanks for your response!

  14. Chari Avatar

    Hi, I know nothing about mosaic beyond what I have read here – which is so informative. I have a 40″ round outdoor iron frame/base table with a glass top inset with a 12″x 6″ section that just broke. I am wondering if it is possible to repair the glass with something (E6000?) and mosaic over the whole table. And if so, can I adhere the tiles directly to the glass top or do I need to use the backer-board (which would significantly raise the table top outside of it’s framed edge.) Thank you.

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Chari,
      I would replace the glass.

      Mosaic tables can be executed on Hardiebacker, which is stronger than regular concrete board. The edges are not crumbly like regular concrete board. The manufacturer doesn’t recommend it for outdoor use because it contains cellulose fibers, which is potential food for mold.

      The key to making it work for an outdoor table top is to paint the side edges and bottom with multiple coats of outdoor paint (oil-based) after the mosaic is finished.

  15. Judy Avatar

    I just tiled a few wrought iron plant stands which have 9 x 9 inch tops with about a half inch metal rim with ceramic one inch square tiles and one with one inch square glass tiles. I used a leveler then adhesive and then sanded grout. Since I leave these tables outside all summer should I use tile and grout sealer? If so, is there a product you recommend?

  16. Andrea Carol-Libman Avatar
    Andrea Carol-Libman

    Hi Joe,

    Thanks for all the valuable info! I want to create an outdoor mosaic table. The table top I have is wrought iron. I’m considering purchasing a laminated wood table top (it’s inexpensive and a good size) to replace the iron top. Do I need to attach hardiebacker or cement board to the laminate table top before tiling? Also, can you make a table with Hardiebacker alone? In other words, no wood at all, just purchase/create a circle of hardiebacker? What would you do in my situation?

    Thanks in advance,


    1. Joe Moorman Avatar
      Joe Moorman

      A laminate wood tabletop would be a disaster for outdoors even in a nominally dry climate. You might be able to use 1/2 Hardiebacker with no plywood underneath depending on how the table base supported the top. If the table base didn’t provide support in enough places, I would probably glue 1/4 Hardiebacker to 1/2 plywood.

      The key to making it work for an outdoor table top is to paint the side edges and bottom with multiple coats of outdoor paint (oil-based) after the mosaic is finished.

      I would have a metal table frame and just set the mosaic top down into it where it could be lifted out and stored each winter.

      Of course you should seal the finished mosaic with multiple applications of a tile and grout sealer.

  17. Suzanne Kirschner Avatar
    Suzanne Kirschner

    HI Joe! I enjoy your posts and they give me great inspiration! I have a small wooden table used inside, 13″ x 22″ with the edge beveled below the top surface leaving the very top above the bevel about 1/8″. The top surface is actually 12 1/2″ x 21 1/2″ if this makes any sense. I would like to tile the top of this with 3 8″ x 8″ tiles and fill in the rest with smaller pieces and preserve the beveled edge. Would I still need to use hardi board on top of the table? I had another question about leaving the edge exposed or using tiny chips of tile on it. One thought was to use a grout on the outside edge colored to match the dark wood of the table. ?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Suzanne,
      Thanks! If the table is indoors, there isn’t any reason to put a tile backer on first.

  18. Sue Avatar

    Hi Joe, great site and information!

    I have a huge concrete freestanding tank that I’ve decommissioned. My plan is to take the roof off and cut it down on one side so you can sit in it. I hope to
    mosaic a design on the walls. Will all ceramic wall tiles cope outside in the weather? And if not, how do I tell which ones will manage outside? I’ve heard something about them freezing. We don’t have snow here, but definitely some icy days.

    Thanks for any help, Sue

    1. Natalija Moss Avatar
      Natalija Moss

      I would strongly recommend using glass tiles for an outdoor project like this because they don’t get affected by ice or frost. Unglazed porcelain is probably okay. The ceramics you really need to avoid are ones that are glazed. The glazes like to crack and pop off when frozen.

  19. Katrina Avatar

    I want to make a very long-lasting, artistic and beautiful, mosaic cover that will rest on top of, and disguise, my existing septic tank lid. It is very likely that people will stand/walk on it. The septic tank lid cover will also need to be light enough that it can be lifted onto its edge and rolled to the side for access to the septic tank lid.

    I am brand new to creating mosaic art. Will you please advise me on the very best materials to use for this creation?

    1. Joe Moorman Avatar
      Joe Moorman

      It’s hard to say not knowing the diameter of the lid.

  20. Dan Costello Avatar
    Dan Costello

    If you are still taking questions, I have one that I need help with. I purchased a round Mosaic table top (48″ dia) for my patio 12 years ago. Many tiles have fallen off and so I removed all the stone from the base. I am not sure what kind of base I have but think it is a 2.0″ foam core backer board as the round edges look to be porous and soft material. It appears that there was a 1/8″ thick thin set on top of that which I have also chipped off. Assuming I have identified the foam core backer board correctly, what base would you recommend I put down before installing new tiles? The current surface is white and very dusty – how should I prep that before putting down a base? New to this but excited to get started.

    1. Joe Moorman Avatar
      Joe Moorman

      If that surface is merely dirty, then wash it. If it has degraded, then it will need replacing. If it is merely chipped, then you can patch it with thinset mortar.

      FYI: A porous concrete material or plaster material with bubbles in it is different from foam-core backer board.

  21. Michelle Avatar

    I want to make an outdoor mosaic table out of tile pieces from the beaches of Mexico. I live in a windy area and was considering using epoxy instead of grout–laying out the pattern and then pouring the epoxy over it. I am worried about yellowing. Do you have any solutions for me?

  22. Tracey Avatar

    I have a small glass top outdoor table that I want to mosaic with glass pieces for the design. What’s the best glue to use-I mostly use weldbond for all of my indoor mosaics. Also, can I use a sanded grout, or is there a clear resin that would work? Thanks!

    1. Joe Moorman Avatar
      Joe Moorman

      Thinset mortar and foam-core backer board are used. Clear resin isn’t archival and doesn’t age well.

      1. Sheena Avatar

        Hi Joe, you are an incredible human for taking the time to answer questions presented so many years after your initial post. Thank you for all your help.
        My wife and I just fell into mosaics and there is no going back! 🙂
        Although this post is for outdoor tables, I do have a question about backing for an indoor (potential outdoor) vertical mosaic piece we have made of my wife’s soccer team emblem. We secured the tiles on A/R resistant drywall mesh with Weldon’s glue in order to follow the design underneath the mesh. Now we have to find a way to secure the mesh design to a vertical surface. We initially bought plywood and a sealant but discovered hardy & wedi board after continued research (both if which you have noted in your responses).
        We purchased adhesive for backsplash tiles but from your answers sounds like we would attach the meshed tiles to the board of our choice with thin set mortar and then grout the glass tiles with sanded grout. I am unsure if I want the piece to go in or outside so want to use the materials for longevity verses an easy completion.

  23. Nancy Avatar

    Dear Joe, I am a little puzzled as I learned to set stone and smalti directly into concrete, with no mortar, grout,or glue (beyond a water soluble adhesive, on the cartoon, using the indirect method). I can understand the need for those if you’re attaching tesserae to a base, but if casting are they necessary? I don’t recall using a sealant either. It’s been a few years…we have some garden ornaments that have weathered well, brought in for the winter. I hope to do some larger pieces that may need to stay out. This is New England, with freeze thaw cycles all winter. I’d thought to use mixed crockery and glass. Your comments/ advice appreciated.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.